Aircraft with controllable sustaining rotors



' y 1941- J. DE LA CIERVA 2,

AIRCRAFT WITH ,CONTROLLABLE ,SUSTAINING ROTORS Filed Oct. 10, 1938 5 Sheets-Sheet 1 20, 1941. J 5 LA c v 2,242,457

AIRCRAFT WITH CONTROLLABLE SUSTAINING ROTORS Filed Oct. 10, 1958 5 Sheets-Sheet 2 mvazgoa BY Aims/wars ATTORNEYi y 1941- J. DE LA CIERVA 2,457

AIRCRAFT WITH CONTROLLABLE SUSTAINING ROTORS Filed Oct. 10, 1938 5 Sheets-Sheet 3 ii i5 i6 J2 ,Z/ U

l 1 w L N w 1 2/ 2; 22

, 27 I Z9 AL/ INVENTOR. 41 A m ATTORNEYJ'.

May 20, 1941. J. DE LA CIERVA AIRCRAFT WITH CONTROLLABLE SUSTAINING ROTORS Filed Oct. 10, 1938 -5 Sheets-Sheet '4 INVENTOR. @ww,

ATTORNEYS.

May 1941- J. DE LA CIERVA 2,242,457

AIRCRAFT WITH CONTROLLABLE SUSTAINING HOTORS Filed Oct. 10, 1938 5 Sheets-Sheet 5 INVENTOR.

Amnv/smmfis BY WYMM A'ITORNEYJ I Patented May 20, 1941 AIRCRAFT WITH CONTBOLLABLE SUSTAINING BOTORS Juan de la Cierva, deceased, late of London, England, and Madrid, Spain, by John Josselyn, London, England, and Reginald Blake, Aldwych, London, England, administrators, assignors, by mesne assignments, to Autogiro Company of 7 America, a corporation of Delaware Application October 10 1938, Serial N0. 234,192

In Great Britain November 2, 1937 4Claims.

The present invention relates to aircraft with controllable sustaining rotors. and more especially to an improved rotor for such aircraft, wherein the rotor turns about a generally upright axis, the thrust line of the rotor being con-' trollable in flight; and while useful in machines having normally power-driven rotors the invention is particularly advantageous in normally movements of the blade but at the same'time or eliminating the disadvantage-just described. A further object of the invention is the provision of an improved rotor enabling the use of a lower solidity, i. e., ratio of blade area to I also area, to be obtained than hitherto usual,

autorotated rotors, which latter may, however,

have a disconnectible drive from the aircraft power plant or suitable auxiliary power plant.

One of the primary objects of the invention is to minimize vibrations in, and the transmission to the controls of undesirable forces and motions from, a controllable rotor, and .at the same time to substantially simplify the rotor construction.

Another object of the invention is to minimize or eliminate the necessity for yielding or resilient restraining devices at the blade pivots. In prior constructions, wherein the rotor comprises a plurality of blades each'pivotally mounted by one or more pivots it hasbeen quite customary to provide, in addition to limiting stops, automatic resilient devices and/or damping devices to restrain the movements of the individual blades on their pivots during flight operation and also to cushion the blades during starting and braking of the rotor and when taxiing on the ground. If not carefully adjusted, and maintained in accurate adjustment, such restraining devices are apt to cause undesirable oscillations or vibrations in the rotor and upon the manual control mechanism by which the thrust line of the rotor 'is controlled. While the present invention in. no way precludes the use of such restraining devices if desired. it is designed to render the use of them unnecessary in most cases,

or to render their adjustment a less critical matter.

More specifically, it is an object of the inven-' tion to minimize or overcome certain jerky motions which were imposed upon the rotor mount, the controls and the machine as a whole in certain machines as heretofore constructed. By way of explanation, in some multi-bladed rotors, as heretofore employed, the blades have been given a large degree of freedom for lag and lead movements in the path of rotation, with the result that either when starting up the rotor or when moving in forward flight, an excessive lag of one blade could coincide with an excessive lead of another blade, with resultant heavy vibrations and undesirable loads on the rotor and its control. The present invention contemplates preserving freedom for substantial lag and lead and at the same time allowing the structure to besimplified and the overall dimensions of the rotor to be reduced, particularly for purposes of parking or storage.

Broadly, the present invention is characterized by the controllable rotor having only one blade, which is suitably counterweighted and pivotally connectedto a hub member.

According to a feature of the invention the pivotal connection of the single blade and oounterweight to the hub, includes at least one pivot whose axis is generally transverse to the radial axis of the blade and lies approximately perpendicular to the hub axis or slightly inclined to a plane perpendicular-to said Such a trans: verse pivot permits flapping of the blade but is preferably inclined to the radial blade axis in such a way that upward flapping of the blade is accompanied by a decrease of pitch angle of the blade, 1. e., the pivot axis makes an acute angle with the radial blade axis ,on the leading side of the blade. "In this manner, change of blade pitch angle is positively inter-related with the arcuate swinging of the blade, and the pitch variation is determined by aerodynamic forces. v

If the pivot axis is slightly inclined to the plane perpendicular to the hub axis the inclination is preferably such that the prolongation .of

, the pivot .axisJying on the leading side of the blade is inclined upwards with respect to the plane perpendicular to the hub axis.

In one preferred constructional arrangement according-to this invention the single blade and its counterweight are rigidly connected to one another and are attached tothe hub by means of a single pivot whose axis intersects the rotational axis of the hub at right angles and isinclined to the radial blade axis at an angle of about on the leading side of the blade.

The invention also includes alternative con-- structions in which the single blade and the counter-weight are independently pivoted to the to a balance member which is in turn connected to the hub by a single central, pivot. To secure various desired operating results, the axes of the several pivots interconnecting the blade, the counterweight and the hub, in such constructions, may be similarly or differentially inclined both to the radial blade axis and to the plane perpendicular to the hub axis and may intersect the hub axis or be offset therefrom. In one such alternative construction the blade and the counterweight are independently pivoted to the hub about parallel axes equally and oppositely on the leading sideof the blade with respect to.

the plane perpendicular to thehub axis so'that the projection of the blade pivot axis on the.

plane containing the hub axis and at right angles to the radial direction of the blade. axis makes an angle of about 7 /2 with the plane perpendicular to the hub axis.

In what follows a sustaining rotor aircraft embodying a single-bladed rotor according to the invention, together with certain modifications, are described, by way of example only, with reference to the accompanying drawings.

.Inthedrawings:

Figure 1 showsin side V embodying the single-bladed controllable sustaining rotor according to the invention;

Figur 'zis a view of the same in plan;

Figure 3 [is a central longitudinal sectional elevation of the rotor head to an enlarged scale;

Figure 4 is a broken partial plan view showing the rotor head and the counterweight;

elevation an aircraft ing control column C universally pivoted at C1 on the pylon structure P and again" universally pivoted at C2 1 to an extension 0': of the rotor headstructure, the connection of which is shown in Figure 3,

Referring now to Figures 3 and 4, the upper part of the mast Pl. carries a universal pivot means comprising'a trunnion block 24, having pairs of trunnions 25, 26, the trunnions being .pivoted in the mast P1 and the trunnions 20 being pivoted in the rotor axis member 23 embracingthe mast. The lower partof the axis member 23 takes the form of an apertured plate and is provided with a socket 33 in which is secured the extension C: for connection to the control column as shown in Figure 1. The member 23 also includes a flange or bracket I'Lto which is secured a housing 28 in which the upper end of the upright shafting S2 is supported in bearings, of which one is shown at II. The shafting S2 terminates upwardly in an extension 30 supported in thehousing 28 by a The upper part of thehub member I! is pro-- vided with a pair of brackets l9 apertured at Ila Figure 5 is a detail viewv in section taken along the line 5-5 of Figure 4; I v

Figure 6 is a detail view in section taken along the line 6-6 of Figure 4;

Figure 7 is a fragmentary view similar to,

Figure 4 illustrating a modification;

Figure 8 is a somewhat diagrammatic view in plan showing a modified form of rotor head with single blade and'counterweight;

Figure 9 shows somewhat diagrammatically and to a slightly enlarged scale the showing of Figure 8 as viewed in end elevation from the tip of he,

Figure 10 is a view similar to Figure 8 showing a further modification.

In Figures'2, 4, Sand 10 the direction orgrmtion of the rotor is indicated by a curved arrow.

Referring to Figuresl and 2; the aircraft comprises a body B, propulsive engine or motor M driving a tractor airscrew A, a wheeled undercarriage U, tail wheel 'I', fixed vertical stabilizing 2 surfaces V, fixed horizontal stabilizing surfaces E which may have upturned tips El, a controllablerudder R, and a rotor supporting pylon P to which is secured a central mast or pylon extension P1 supporting the rotor head generally indicated at H. For driving the rotor for starting purposes there is provided transmission mechanism comprising shafting S1 connected to the engine M and upright shafting S: having driving connections to the rotor illustrated in Figures 3 and 4,

the shafting members S1, S: being connected by to receive flapping pivot llb on which is articu lated a rocking member l2 flanged at each end at l3., A single rotor blade i0 is provided at the inner. end of its spar Ilia with a flange I I for attachv ment, asby bolts I la. (one of which is shown), with oneof the flanges ii of the member ii, the

blade being balanced by a counterweight I8 secured, e. g., by bolts II, to a short arm ll provided at its inner. end with a flange ii for attachment to the other flange II of the member ii, the arm ll being aligned with and directed oppositely to the blade ill with respect to the hub viewed in plan.

Though the counterweight is not intended as a lifting element,.yet to minimize dragit may ad'- The axis (indicated by the line ,H). of the single flapping pivot llb intersects the rotational axis of the him at 90", being therefore contained in a plane perpendicularto the axis of the hub, Y

and is inclinedlto the axis b-'-b of the blade and counterweight arm at. an acute angle on the leading side of the blade, as shown in Figured; this acute angle beingpreferably about 60.

The principal component of the flapping oscillation (with associated pitch variation) about the axis .of the pivot lib, when in forward flight,

has a frequency of once per revolution of the rotor blade causes it to cone," i, e.,theradial a'xis of cated together at J1. The rotor head H is uni-.

versally pivoted on the mast Pr as shown in Figure 3 and is controllable by means of a hangthe blade. (hr-bin Figure '4) has a mean inclination above the plane perpendicular to the axis of the hub called the coning" angle whose value is of the same order as that ofthe flapping angle. 7

Since the axis 6-6 of the flapping pivot 18b is perpendicular to the axis of the hub, the motion of the blade theerabout, at least for small values tion taken from the tip of the blade, from which itwillbeseenthattheaxis6-6isinclinedupwards on the leading side of the blade with respect to the plane a-u perpendicular to the hub axis -0. When projected on the plane of Fig- 7 iv-6' or the flappingiand coning angles, takes place ure 9, which is perpendicular to the blade axis approximately in a plane containing the axis oi H of Figure 8, the angle between the projecthe hub, with respect to which the axis of the ime 0 and H is in h ample about path described by the blade tip is inclined b'y 1 he flappin xis were oblique in plan reason of the flapping motion, with the result 5 only, i. e., at an acute angle to the blade axis that the angular velocity 01' the hub and the H. as seen in Figure the blade. when flapangular velocity of the blade about the axis of D p dly. would else be m v g toward a its true path are subject to periodic variation ing position (viewed in plan); u y ntrerelatively to one another. When the rotor is ducing the secondary obliquity, i. e., inclining the operating autorotatively, the hub, by reason or 10 hinge axis upwardly at the forward side or the its negligible moment of inertia compared with blade (asseenin ure t e flapping movethat of the blade and counter eight, experiences ment of the blade can be made to occur in a a periodically varying angular velocity, while the Pl n ant ally cont ining the rotor axis blade and counterweight rotate with substantially n f c a s con a at on of We". as constant angular veloolty about th t axi of here employed, will be sufllcient to introduce their path and n ub ta ti l b ndin m t some la ing movement of the blade upon upin the blade and counterweight arm in the path of rd fl p n a d eading movement upon downmotion are generated, ward flapping, which is in conformity with the There is also, however, a periodio variatio f aerodynamic forces acting on the blade when the aerodynamic drag force operatin approximately machine is traveling in forward flight. Thus in the path of motion and tendin t cause bending stresses are materially reduced.

' riodic variation or the angular velo it f t A further modification is illustrated in Figure blade, These forces are experienced by t blade 10 in wh ch the blade and counterweight are inbut not by the counterweight and they therefore 7 dependently pivoted to a balance member which giveriseto periodic bending momentsinthe rigidis in turn pivoted to the hub. In this instance lyeonnected blade and counter eight These the balance member I'Zx is pivoted tothe hub bending moments and those resulting from second about an axis 5- W is inclined as in the and higher order harmonics or the flapping mopr vi us examples in plan v w (as sh wn in Fi .tlon, may b relieved byjntroducing an additional ure 10) to the radial axis of the blade and counpivot connecting th eormt r i ht r t t terweight so as to make an acute angle on the central rocking member ii, the axis of hi leading side of the blade. As before the pivot pin pivot is orientated primarily for relative lag and the Pivot fi-fl is supp r ed in e rs is int r l lead between the blade and counterweight, said With the hub, as inFigures 3 d pivot axis for example being approximately pargL- The balance member I21: terminates laterally lei to the axis of rotation oi the hub. This modin forks 34 and a which pport pivot pins on flcation is illustrated in Figure 7 i which th which are articulated root members 35 and 36 flange [5 at the root of th counterweight arm n terminating in flanges 31 and 38 for attachment is secured to a flange l3 on a forked member II pectively tothe flanged root ll of the blade ill pivoted to the rocking member I! by means of a and the flanged root ii of the counterweight arm in whose xi n th position shown in Figure 40 ll. The axes of the pivot pins carrying the'root 7 i parallel to th r t tio a axis of t members 35 and 36are respectively denominated Figures 8 and 9 h w a mqdifled construction 6-6 and 6' and these axes are in this examwherein the blade and counterweight are inde- D inclined in the pl n V ew of Figure 10 in the ndently ivoted t on ten i of t huh opposite direction to the axis 8-18 with respect member. Figure 8 shows the modified rotor in to the blade and counterweight axis b-b. The plan, and the hub member is provided at the top axes fifl' H and are m reover inclined th an integral k t member 9 terminating 1 with respect to the plane of the figure, which is laterally in a pair of forks I82, lay, which p rt perpendicular to the axis of rotation of the hub,- i t in n hi h t blade and counterweight and it will be seen by the appearance of the ears aremounted. The flanged root ll of the blade ll l8 and f s that the axis fls is is secured as before to a flange "a of a root memciihed r ly wi h respec t the plane D her a m t on t pivot pin n by t pendicular to the hub axis on the leading side fork and t flanged t lb of t t of the blade as viewed from the tip of the blade, weight arm I4 is seem-ed t a flange no of t whereas the axes 6-6 and 6' are inclined in member m; mounted on t pivot pin carried the opposite direction with respect to the plane by the fork I811. The axes of these pivots are P pe ar t0 the hub axis. As in Figure 8, denoted respectively by the lines 6-6 and 6-6'. the axes H and 6 p a to In the plan view shown in Figure 8 these ax r other, and whereas the inclmatlon of the axis inclined similarly to the axis of Figure 4 at an 4 -8 n the direction shown, i. e., making an acute angle of about to the radial axis H of the 60 angle with the blade'axis on the leading side of blade and counterweight, the acute angle being the blade, is considered to be of importance, the on the leading side of the blade as before. auxiliary axes H and a may be inclined in plan in the opposite direction as shown, or alter- With the object of reducing bending stresses natively in the same direction but preferably at in the blade and counterweight arm, consequent a slightly were! angle being advantageously on the flapping and com movement the'mvot more nearly perpendicular to the blade axis b-b axes 6-6 and 6'6' are slightly inclined, as in'plan View. plane Perpendicular to the rota As regards the inclination of these axes in i -l axis of t This is more Clea-1'19 end elevation the exact values of the respective shown in i ure 9, which hows a V in eievainclinations are largely optional, although it is preferable that the projection of the axes 6-6 and 6'6' on the plane perpendicular to the axis 11-!) are not coincident or parallel with the projection of axis p-s and that the axes 6-6 and are sufllciently inclined in elevation to permit substantialleading and lag ing motions of the blade and counterweight.

It is therefore to be understood that the constructions illustrated in Figures 8 to 10 are given,

single blade of the rotor according to this invention may be made such that ample clearance over the propeller and tail surfaces will be secured under all conditions of tilt of the controllable rotor axis, the-counterweight. presenting no clearance problem, since it traverses a path close to the rotor mounting pylon, its distance from the rotor centre being less than the distance between said centre and the airscrew.

From the foregoing it is thought that without further explanation it will be evident that the objects and advantages set out at the beginning of this specification are secured by the present invention by a construction which is relatively simple and therefore less costly to build and maintain than many of the structures heretofore in use, and notably that the arrangement tends -to minimize undesirable motions and forces in the control stick of an aircraft having a controllable rotor wherein the rotor thrust line is shiftable with reference to the centre of gravity of the craft for control purposes.

It is claimed:

1. For an aircraft, a sustaining and controlling rotor comprising a generally upright hub member, a single sustaining blade radially disposed thereon, pivotal means connecting said blade .to the hub member and providing at least for oscillation of said blade generally transverse its path of rotation, a substantially non-lifting counterweight counterbalancing said blade, controllable means adapted to alter the path of blade movement to shift the thrust line of the rotor for control purposes, said pivotal means comprising a balance member pivotally connected to the hub about an axis generally transverse to the radial axis of the blade and approximately intersecting the hub axis; and pivot means independently pivoting the blade and counterweight to the balance member about axes oppositely spaced from and non-intersecting with respect to the hub axis and obliquely angled with respect to the axis of the pivot connecting on an axis so angled that when viewed in plan form, and of "solidity," the coning angle of the the pivot axis makes an acute angle with the longitudinal axis of a blade at the leading side of the latter and at the outboard side of the pivot axis, and a pivot connecting a blade with said connecting member, the axis of the. last pivot, when viewed in plan, making an obtuse angle with the longitudinal axis of the associated blade at the leading side thereof and at the outboard side of the pivot axis.

3. In an aircraft sustr comprising a hub and blade means, mec a z u for connecting the blade means with the hub including a con necting member pivotally mounted on the hub on anaxis so angled that when viewed in plan the pivot axis makes an acute angle with the longitudinal axis of a blade at the leading side of the latter and at the outboard side of the pivot axis, and a pivot connecting a blade with said connecting member, the axis of the last pivot being located outboard of the first pivot axis and, when viewed in plan, making an obtuse angle with the longitudinal axis of the associated blade at the leading side thereof and at the outboard side of the pivot axis.

4. In an aircraft sustaining rotor comprising a hub and blade means, mechanism for connecting the blade means with the hub including a connecting member pivotally mounted on the hub on an axis intersecting the hub axis and so angled that when viewed in plan the pivot axis makes an acute angle with the longitudinal axis of a blade at the leading side of the latter and at the outboard side of the pivot axis, and a pivot connecting a blade with said connecting member, the axis of the last pivot being located outboard of the first pivot axis and, when viewed in plan, making an obtuse angle with the longitudinal axis'of the associated blade at the leading side thereof and at the outboard side of the pivot axis.

JOHN JOSSELYN. R. BLAKE. Administrators of the Estate of Juan de la Cierva, Deceased. 

